When Ballentine goes to the drugstore to purchase saltpeter, he requests Potassium Sulfate, rather than Potassium Nitrate.
When Ballentine goes to the drugstore to purchase saltpeter, he starts to say Sodium Nitrate, rather than Potassium Nitrate. But does say Potassium Nitrate, so we don't know if it was scripted that way or not.